Exhaust Gas Purification Catalyst Pore Structure Optimization
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Solution Overview
Problem
Existing exhaust gas purification catalysts inadequately store NOx due to non-uniform gas supply through large pores, preventing effective NOx oxidation and storage.
Innovation Solution
An exhaust gas purification catalyst with a substrate, a first catalyst layer for NOx reduction, and a second catalyst layer for NOx oxidation, featuring a specific pore structure with a volume percentage of 2.82% to 8.30% for all pores, where large pores are optimized to facilitate uniform gas supply and enhance NOx storage capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the second catalyst layer contains large pores to facilitate gas diffusion, then gas diffusion paths increase, but gas supply becomes non-uniform and NOx storage performance deteriorates
Solution Approach 1:
The patent changes the pore volume percentage parameter from conventional high values to a specific range of 2.82% to 8.30%, and controls the ratio of large to medium pores to be 2.44 or less. This parameter optimization ensures uniform gas distribution while maintaining adequate diffusion paths, resolving the contradiction between gas diffusion rate and NOx storage performance
Solution Approach 2:
The patent creates different pore size distributions in different regions of the second catalyst layer by controlling the ratio of large to medium pores. This local quality differentiation ensures that gas flows uniformly through the catalyst layer while maintaining sufficient diffusion capacity, preventing both channeling and insufficient diffusion
2Ease of operation
If the pore volume percentage in the second catalyst layer is increased to enhance gas diffusion, then gas distribution improves, but catalytic metal dispersion is reduced and oxidation efficiency deteriorates
Solution Approach 1:
The patent optimizes the pore volume percentage to a specific range of 2.82% to 8.30%, which is sufficient to ensure uniform gas distribution but not excessive to cause catalytic metal aggregation. This precise parameter control maintains both gas distribution uniformity and oxidation efficiency
Solution Approach 2:
The patent creates a composite structure in the second catalyst layer combining controlled pore spaces with catalytic metal particles. The optimized pore structure provides uniform gas distribution while the remaining matrix maintains high catalytic metal dispersion, achieving both gas distribution uniformity and oxidation efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The catalyst achieves superior NOx storage and oxidation efficiency by ensuring uniform gas distribution and increased surface area, leading to improved NOx purification rates.
Implementation Method 1
a second catalyst layer containing a catalytic metal for NOx oxidation and formed on the first catalyst layer
Implementation Method 2
a first catalyst layer containing a catalytic metal for NOx reduction and an NOx storage material and formed on the substrate
Implementation Method 3
the volume percentage of all pores in the second catalyst layer is 2.82% by volume to 8.30% by volume, and the value obtained by dividing the total volume of all large pores having a pore volume of 1000 μm3 or more by the total volume of all medium pores of having a pore volume of 10 μm3 to 1000 μm3 is 2.44 or less
Data Source
AI summary
An object of the present disclosure is to provide an exhaust gas purification catalyst demonstrating superior storage of NOx contained in exhaust gas.The exhaust gas purification catalyst of the present disclosure has a substrate, a first catalyst layer containing a catalytic metal for NOx reduction and a NOx storage material and formed on the substrate, and a second catalyst layer containing a catalytic metal for NOx oxidation and formed on the first catalyst layer. In the exhaust gas purification catalyst of the present disclosure, the value obtained by dividing the volume of all large pores having a pore volume of 1000 μm3 or more by the total volume of all medium pores of having a pore volume of 10 μm3 to 1000 μm3 in the second catalyst layer is 2.44 or less.